Now that I've had a chance to sleep, here's a solution that accepts either a count or an arrayref.

sub genIterator {
    my ($len,$array) = @_;
    $array = [0..$array-1] if $array =~ /^\d+$/;
    die "Don't know what to do with $array" unless ref $array eq "ARRA
+Y";
    my @list = ();
    return sub {
        return undef unless @$array;
        if (@list < $len) {
            push @list, 0;
        } else {
            $list[-1]++;
            while (@list && $list[-1] >= @$array) {
                pop @list;
                $list[-1]++ if @list;
            }
        } 
        return @list ? join("", @$array[@list]) : undef;
    }
}
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